Connecting circuits



Patented July 28, 1925.

UNITED STATES n 1,547,577 PATENT OFFICE.

CLARENCE B. FOWLER, OF NEW YRK, N. Y., ASSIGNO'R TO WESTERN ELECTRIC C OM- PANY, INCOBPQRATED, OF NEV YORK, N. VY., A CORPORATION OF NEW-YORK.

CONNECTING CIRCUITS.

Application led August 29, 1923. Serial No. 659,877.

To @ZZ whom t may concern Be it known that I, CLARENCE B. Fowmia, a citizen of the United States of America, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Connecting Circuits, of which the following is a full, clear, concise, and eXact description.

This invention relates to circuits for use in telephone exchange systems for interconnecting subscribers lines, and more particularly, to connecting circuits for use in eX-k tending connections from subscribers lines terminating in a plurality of connecting terininals.

Among the objects of the invention is to simplify and improve the circuit arrange-r ments of such connecting circuits soA that only one connecting circuit can be operatively connected to a calling line Yat a. time.

In accordance with one feature of theinvention there is provided a testing circuitv common to a plurality of connecting circuits having a pair of polarized relays, rone of which operates if an operator connects a connecting circuit to an idle line to permit the connection of an operators telephone set to the line, and the other of which oper` ates if a busy line is seized by the operator to prevent the connectionA of the operators telephone set to the line. Another feature of the invention resides in the provision of signaling apparatus in a circuit arrangement of this character for indicating to the operator the busy condition of the seized line. v

In the drawings, W

Fig. l shows a calling station A and a called station B with associated'line circuits, one of a plurality of connecting or link circuits C, which may be used to interconnect such stations, and an operators telephone set and testing circuit O'cominon to a plurality of the link circuits.

Fig. 2 shows diagrainmatically an unbalanced Vheatstone bridge circuit in which the controlling relays of the testing circuit are connected when a second `link circuit is connected with a. line withwhich another link circuit is already connected. y

Each of the stations A and B is shown terminating at the central office in a plurality of answering jacks and a multiple jack. Each answering jack has a signaling device associated therewith.v rIhe answering jacks and their associated line lamps for 1a station terminate at different operators positions. Multiple jacks, only one of which is shown in the drawing, may appear at each operators position.; Y

In the following detailed description. it will be assumed that' a subscriberl at the station Ais the calling subscriber and'that a subscriber at station B is thecalled subscriber. l

Upon initiating a call, the subscriber at station A removes the receiver from. the Y switchhook and establishes an energizing circuit for line relay 3 which operates. Belay 3, in operating, completes a circuit eX tending from grounded battery through the n `filaments of the line lamps 8 and 9, which lamps' are located in front of different oper-y ators at thel central ottica-any one of which operators may answer thel call. The lamps e are illuminated notifyingl all the operators that a call is awaitingattention.V f

It will be assumed that at this time the roperator at thel position'at which lampv 8 is located is free to handletthe incoming call. This operator, therefore, inserts the plug lllassociated with the cord circuit C into jacklQ.` located at her position rand as-` sociatedwitli the calling subscribers line.4

Upon the insertionv of plug Il into jack 12,`a starting relay 20- common to the link circuits of the' operators position, operates over a circuit from ground,` through the windingof cut-0E relay 4, sleeve contacts of jack 12 and plug 11,.winding and con tact 64 of relay 14, contact 65 of relay 33, conductor 7 5, contact 66 of relay 31, -contact 67 of relay 32, winding of relay 20, contact 68 of relay 35 and contact 69 of relay 3l to grounded battery. Relays l and 14. included. in this circuit do not receive sufficient current at this time to operate. Relay 20, in operating causes the operation of relay 32. `Relay 32 in attracting its inner left hand armature, opens at Contact 67 a shunt path'norinally connected around the polarized relays 30 and 40, .connects ground through contact 72of relay 32 between resistance 19 and relay. 20, and connects groundedy battery through resistance 18 and lOl) contact 7 8 of relay 32 between relay 4Q and resistance 19. With! relay 32 operated and the position at which lamp 9 is located attempts to handle the call upon noting the illumination of lamp 9. 1t is to' be understood that the operator at such position attempts to handle an incoming call immediately after the first operator has answered a call, otherwise the lamp 9 would have been extinguished upon the insertion of plug 11 into jack 12.

The second operator,` having a cord and associated test and operators circuit identical with the one shown in the drawing, inserts the plug 11 thereof into jack 50. The sleeve of jack 50 being multipled with that of jack 12, now has a busy potential connected thereto owing to the insertion of plug 11 of the original cord into jack 12 by the first operator. The potential on the sleeve of i jack 12 has been provided from the battery associated with the sleeve of the plug ol' the original cord.

Upon inserting plug 11 of the second cord into jack 50, an energizing circuit is established for relay 2O over a path extending from ground, through the winding of cutoff relay 4, sleeve of jack 50 and sleeve of the second cord 11, winding and contact 64 of relay 14 of the second cord, contact 65 of relay 33 of the second cord, lcontact 66 of relay 31 of the second cord, contact 67 of relay 32 of the second cord, winding of relay 20 of the second cord, contact 68 of relay 35 of the second cord and Contact 69 of relay 31 of the second cord to grounded battery. Another path for current'through the winding of relay 4 to ground extends through the sleeves of jack 12 and plug 11 and winding of relay 14 to battery potential, but relay 2O ofthe second cord is of the sensitive type and operates in the parallel branch t0 battery extending to the second cord. Relay 2O of the second cord in operating causes the operation of relay 32 which closes at its contact 7 2 the circuit previously traced for holding relay 20 operated. Due to the fact that a plug at another operators position has been previously inserted into a multiple of the jack 50, the current flowing through the polarized relays 30 and 40 is in a direction opposite to that which it was when the line was idle and is in such a direction as to cause the operation of polarized relay 40 only. The reason that the current flows in a reversed direction at this time is due to the fact that an unbalanced lVheatstone bridge arrangement is formed in which the sleeve circuit of the first connected link circuit and resistance 1S associated with the second link circuit form two adjacent arms with battery connected between them, and resistance 19 0f the second link circuit and cut-ofi' relay 4 form the two other adjacent arms with ground connected between them, and in which relays 30, 40 and 14 of the second link circuit forni the bridge arm.

' lhis unbalanced Wheatstone bridge circuit 1s sho-wn 1n Fig. 2, wherein the apparatus associated with the second connected linkl circuit is indicated by reference charactersl without primes. It has been found that with the values of resistance indicated hereinafter this current reversal exists not only when a second operator plugs in a calling line but also when a plurality of operators plug in a calling line after the rst operator has obtained the connection. f

The operation of polarized relay 40 associated with the second connected link circuit causes the operation of relay and establishes a holding circuit for relay 32 through the right hand winding thereof. Relay 35 in operating releases relay 2O and opens contacts in the leads from the operators telephone set extending to the listeningy key 42 of the second connected link circuit and the listening keys of the other link cir-- cuits .at the same operators position. closing of the alternate contacts of relay 85 connects a source of tone supply 80, to the receiver 81 toindicate to the operator the busy condition of the calling line orthe fact that the call has already been answered by another operator. The resistance of the common apparatus of the test circuit is at this time of such a value as to prevent the operation of marginal relay 14 of the secondl link circuit and the operators telephoneset therefor is barred.

The operator, noting the tone signal, removes the plug 11 at the second operators position from jack 50, whereupon relay 401 releases. Relay 40,iretracting its armature, opens the holding circuit for relay 32, which then releases. Relay 35 is of the slow to release type and retracts its armature an interval after its energizing circuit is opened at the contacts of relay 40.

According to one way in which the invention has been practiced al1 operators except the one first to answer a call are barred from the connection when a 24 volt battery is employed and the resistances and relays employed in association with the testing circuit have the values set forth below.

Relay 4, 34 ohms; relay 14, 90v ohms; relay 30, 42 ohms; relay 40, 42 ohms; relay 20, 1800 ohms; relay 31, 25() ohms for the left hand winding.'

Resistance 19, 15 ohms; resistance 17, 170 ohms; resistance 18, 125 ohms.

Obviously, other resistance values for the apparatus involved in the test and line circuits may be employed.

The invention claimed is:

1. The combination with a number of telephone lines extending from substations to multiple terminals at a central oliice, of a The plurality of linkfcreuits. each, havinaaliiam ual connecting terminal, telephonie annata,

ins @Ommen i0 saisi link. eifliiis, bleekiig mechanism for .rendering Said, telephonie. apparatush inert, means te, Said liilli Circuits for oontrollingsaid blocking ineclianisin, and a circuit completed for said ineens` in responset@ the. emineciioiiei elle @if said. manual connecting terminale iQ One el the.

terminals Qi abusy lilie- 2. The cqnibination with amueblar Qi' telar. Pheiielnes extending from SubStaiiOiiS le. multiple ieriiiirialsV ate- ,Ceiiifel Qiiiee, 0f a plurality @if linknircuits @achieving an enf sWQlng and calling plug, telephonie apparatus cornrnon to, ,said linl circuits, l blocking mechanism for rendefiigad lelalllltli. aP:

paratusA inert, means common to said linkV circuits for ontrpllin,g.` saihblockling mecha--` mism, and a circuit completed i'ei" eail ineens.

as oneefsaid. aiieweriie Pleaseiigaees ille terminalfoi. a busy line.

3,111 a .teleiiliene System, a Calliesliiie, an` operators telephone set, and. a oordcir- Cuit for connection Witli'said line proiiided with, testing apparatus including a pair of polarized relays, one off said relays operating` if the line isidle to permit the connes, tion of theoperatorfs set to the cordeirc'uit, and the other of'said relays operatingfi-f the line islousy to prevent the Kooniieetion of tlize operators set to the cord circuit.

4;. Ina telephone system, a calling line, an operators telephone set, and aI oord` circuit forV connection` with said lineproyided *Witli` testing apparatus inoludingapair of'polarized relays, one of said relaysloperatingi the line is idle to permit the connectionl of the operators set to the cord cireuit and. theother ,of` said relays operating if tlie is .lousyto prevent the connection, ofthe op-i erators setto thepcofd circuit aiid.;tofcn`1`ie`ct a tone to.the'operatorsftlplle,Set.M" l

5. In a telephone. system, ai calling line terminating in a conneeting terminal, oord Circuit `for therewith, anppera' tors telephone equipment,` for, said Cord cir-V cord oirouit'inoluding fpair of; polarized! relays, asource ofcurrent, and.V circuit'con neciieas .arfaiiseflel that' eil'ireiii frein ,Seid` sourceloWs 1n a dlreetion to operate oneoif Saiafreiays, iftne iinejsezed is raie, 'to per; Init the oonnectionfof the D0per"tfo1"s` tele-` phone equiprnerittothe calling'line, and in another directiontp operatefanotliei1 of said relays, if tlieflinefseiied louzsyftr prevent to the line. Y 6. In a telephone-system, a, calling line the connection of tlie foperatois terminating in a'plurality'of connecting ter? n v u l .4 :in: n i minals, a oord `circuit for connection with one oisaid terminals, anl Qperators telephone equipment',` for 'said cord circuit, aA

testing circuit associated, said lc'ordeir.. cuit. including a pair of polarized rel f source of. current, anllcirouit connectionsfarranged so that.'fcuifrent,"ligorri` said source` flows 1u a direction Joo.,operate one of saidy relays, ifftlie lineh idlefto periiiit the connection of the V',operatorsf telephone equipment to the Calling andin` another flireiieii i0 .Operate @ether-effen@ llarfs, ii,` the line Seized iS. busy, te rfrent the con# 

